iPhone: If you have a particularly heavy foot while driving, you might want some motivation to drive a bit slower. Free app Slow Down monitors your speed, and slows down your music when you start driving over the speed limit.

Slow Down taps into your iPhone's music library and lets you create a playlist for driving. Once you start playing, you can select one of three speed limits (50, 90, or 120 kilometers per hour, which equals roughly 30, 55, or 74 miles per hour, respectively) for it to monitor. As you drive, it will check your speed and slow down your music if you go over the selected speed limit. If you go 10 kilometers per hour over the speed limit, it'll stop your music entirely.

It's a pretty cool idea for an app, despite the limited speed limits available to you (especially for US residents, where 55 miles per hour is a less common speed limit than, say, 45). Whatever you do, just don't fiddle with the app while you're driving—that'll defeat the whole purpose.